#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>

int main() {
    int n;
    int num[n];
    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
        scanf("%d", &num[i]);
    }
    int sum = 0;
    int x = 0;
    for (int i = 0; i < n; i++) {
        sum += num[i];
        sum -= x;
        x++;
    }
    printf("%d", sum);
    return 0;
}